JPS6289711A - Acrylonitrile polymer fine particle aggregate and production thereof - Google Patents

Abstract

PURPOSE:To obtain the titled fine particle aggregate useful as a filler for electrostatic recording material, etc., having low hydrophilic nature, improved weather resistance, whiteness, etc., by grinding acrylonitrile aggregated polymer particles satisfying a specific condition, classifying and pulverizing. CONSTITUTION:Firstly, polymer particles which have >=95wt% copolymerization amount of acrylonitrile, 1-8 reduced viscosity, 0.1-2mu particle diameters and contain no sulfonic group obtained by aqueous suspension polymerization method are aggregated, to give acrylonitrile aggregated polymer particles having >=10mu volume-average particle diameter. Then, the particles are ground and classified to give the aimed fine particle aggregate having 1-5mu volume-average particle diameter and <=0.05% number content of particles having >=8mu particle diameter. The grinding of the polymer particles is preferably carried out by blowing jet air flow from a jet air flow inlet 11 to a grinding zone 13 and making raw material particle collide with themselves while rotating them.

Description

[Detailed description of the invention]

[Field of Industrial Application] The present invention relates to uniform fine particles made of a polymer mainly composed of acrylonitrile that can be used in place of inorganic fillers such as titanium oxide, silica gel, kaolin, and clay, and a method for producing the same. be. Inorganic fillers such as titanium oxide, silica gel, and kaolin have excellent chemical resistance and weather resistance, and their micronization technology has advanced and is used in a variety of fields of application. However, due to the manufacturing process, these inorganic fillers are strongly acidic substances, and when used as a polishing filler, long-term storage of paper may cause yellowing of the paper and deterioration of paper quality. It has become a major social problem. In addition, with the increasing use of paper in the information society, the weight of paper due to the weight of added inorganic fillers has become a major problem in the printing process and transportation field. Attempts have been made to improve the various problems mentioned above by using organic fillers instead of . Inorganic fillers are also added to the dielectric recording layer of electrostatic recording paper in order to give the layer surface roughness, but since these inorganic fillers are hydrophilic substances, It is known that this impairs the insulation properties of the body layer, leading to a deterioration of its electrostatic recording properties, and it is desired to develop a filler that does not cause such disadvantages. [Prior art] Japanese Patent Publication No. 49-31753 discloses that solvents that do not dissolve polyacrylonitrile, such as methanol, ethanol, phthanol, cyclohexa/, toluene, xylene,
A method has been disclosed in which acrylonitrile kN is combined in a solvent such as water, and the resulting polymer is subjected to a dispersion treatment using a physical dispersion method such as a ball mill or a roller mill to obtain a uniform particulate polymer. The average diameter of the acrylonitrile polymer particles obtained by this method is usually irregularly shaped particles of 10 to 40 μm, as shown in Figure 1 (a), and these polymer particles are processed by ball milling or rolling in a solvent. Although it is possible to obtain particles with an average particle size of approximately 6 to 20μ by physical dispersion treatment such as a mill, it is difficult to obtain polymer particles with an average particle size of 5J1 or less, which is required for organic polymer fine particles. The particle size distribution is also extremely wide, ranging from 1 to 20 microns, and due to the characteristics of the optical filler, it is extremely difficult to make the particle size distribution uniform by classifying organic polymers of this size. In Japanese Patent Publication No. 57-31732, the cation concentration is 003.
~3 g ions//--H2Ofx An unsaturated compound mainly composed of acrylonitrile gold is polymerized in water with stirring at a temperature of 12 at least 2 x 1
After forming an aqueous dispersion of the polymer moiety in a substantially molten state with a particle size of 1 to 2000 μm and forming an aqueous dispersion of the polymer moiety in a substantially molten state with a particle size of 1 to 2000 μm.
A method for producing a cooled acrylonitrile-based fine particle N coalescence is shown. According to this method, fine acrylonitrile polymer particles with a uniform particle size can be obtained, but since it is necessary to form molten droplets of one acrylonitrile thread in an aqueous medium, co-N of acrylonitrile in the acrylonitrile polymer is required.
For the 9 ratio, it is necessary to keep the weight of 93 times lower than 93 times. Therefore, problems have been pointed out that the heat resistance of the obtained acrylonitrile thread polymer particles is not sufficient and that the amount of white charcoal required as a filler is not sufficient. Furthermore, the acrylonitrile polymer particles obtained by this method contain 2×10 sulfonate groups or salts thereof.
-S mol/f polymer is contained in a ratio of more than The appearance of fine powder of acrylonitrile-based polymers with low levels of acrylonitrile is desired. [Problems to be solved by the invention] With the technology that has been developed as an organic filler that can be used in place of inorganic fillers, it is difficult to create fine organic resin particles with an average particle size of 5μ or less and no coarse particles. Either this was extremely deceptive, or only fine particle aggregates could be made from specific resins containing large amounts of hydrophilic or polar groups. The present inventors conducted a study on ultrafine pulverization of the acrylonitrile polymer described in the paper, and found that a specific fine powder obtained by crushing and classifying an acrylonitrile polymer with a specific composition was used for electrostatic recording materials, etc. It was discovered that it exhibits excellent effects as a filler, and the present invention was completed. The gist of the present invention is that the copolymerized amount of acrylonitrile is 95% by weight or more, the polymer is made of a polymer that does not substantially contain sulfonic acid groups and has a reduced viscosity of 1.0 to aO, and has a volume average particle diameter of 1 to 1. The present invention provides an acrylonitrile polymer fine particle aggregate and a method for producing the same, characterized in that the number content of particles having a diameter of 5μ and exceeding 8μ is 1105L4 or less. The monomer constituting the acrylonitrile polymer of the present invention contains acrylonitrile of 95% or more by weight, and the reduced viscosity (polymer concentration The viscosity (measured at °C) is in the range of 1.0 to &0. A polymer with a copolymerized amount of less than 95% by weight of acrylonitrile constituting the fine powder of the present invention exhibits thermoplasticity and lacks hardness and chemical resistance compared to the acrylonitrile-based polymer used in the present invention. As a result, white discoloration, weather resistance, and light resistance, which are essential requirements, will be low. Acrylonitrile polymers with a reduced viscosity of less than 1.0 tend to be brittle'j)9,
On the other hand, it is difficult to form uniform fine particles with a particle diameter of 5 μm or less from a polymer having a reduced viscosity exceeding aO. The acrylonitrile polymer constituting the acrylonitrile polymer fine particle aggregate of the present invention should contain substantially no sulfonic acid groups, and in particular, should have a content of 5 x 10-s equivalent/l polymer. , more preferably 2X
It is necessary that the sulfonic acid group content in the acrylonitrile-based polymer is 5×
Acrylonitrile polymer powders made from polymers larger than 10-S mol/l polymer tend to be highly hydrophilic, and when used as paint additives, tend to impart hydrophilic properties to paint films. is strong and is likely to cause deterioration of the paint film. Furthermore, when used as a paper additive, the paper quality itself becomes acidic and the paper quality deteriorates by 17 tons during long-term storage. Furthermore, when used as a filler for electrostatic recording paper, it is impossible to produce electrostatic recording paper with excellent image density and resolution. From this point of view, the acrylonitrile polymer used in the present invention should contain substantially no sulfonic acid groups, more specifically, the amount of sulfonic acid groups should be 5 x 10-s.
To 1/f poly, especially 2 x 10-5 t/l
It is preferable that the content of the polymer be sufficient. Other copolymerizable vinyl monomers that can be copolymerized with acrylonitrile at a ratio of 5 mft% or less include methyl methacrylate, methyl acrylate, ethyl acrylate, vinyl chloride, vinyl acetate, styrene, α-methylstyrene, maleic acid, and maleic acid amide. , N-phenyl-substituted maleimide, etc. The acrylonitrile polymer imitation particles obtained by the present invention have a volume average particle diameter in the range of 1 to 5μ, and the number content of particles with a diameter exceeding 8μ is (105% or less, preferably,
It is necessary that the volume average particle diameter is in the range of 1.5 to 4μ, and the number content of particles with a diameter exceeding 8μ is no more than 2%. When aggregates of fine particles with an average particle diameter of less than 1 μm are used as a matting filler for paints or paper coating agents, they cannot produce the expected matting effect and are not used as paper coating agents. It becomes difficult to form a writing surface with excellent writing and stamping properties. On the other hand, polymers of acrylonitrile polymer particles with an average particle size exceeding 5μ have a particle size that is too rough, and coating films obtained using fillers with such particle diameters have noticeable surface roughness, resulting in coating films with excellent appearance. Unable to fully form. Additionally, coated paper made using such acrylonitrile polymer as a filler for paper coating also has good writability,
Good imprintability cannot be obtained. Such a tendency becomes remarkable when particles having a large diameter exceeding 8 pk are contained in an amount exceeding 105%. For example, assuming that the acrylonitrile polymer particles are spherical, the maximum cross-sectional area of particles with a diameter of 2.5 μm is 4.5 μm.
9μ2, whereas the maximum cross-sectional area of a particle with a diameter of 8μ is 5
[12μ2, the maximum cross-sectional area of a particle with a diameter of 10μ is 7a5μ2
This falsifies the fact that while the particle diameter expansion rate increases by Z4 times and 4 times, the cross-sectional area rapidly expands by 1α5 times and 16 times, respectively, and particles exceeding 8μ ( 10ss
Aggregates of fine acrylonitrile polymer particles with an average particle diameter of 1 to 5 μm that exceed t will lose their properties as fillers. As mentioned above, in order to improve the custom-made acrylonitrile polymer fine particles containing only a small amount of large diameter particles, the content of particles with a diameter exceeding 8μ is tα 05% or less,
If it is preferably 1102 or less, its characteristics will be significantly improved and it can be used as a companion, but it is especially suitable for electrostatic recording materials that are required to have a recording density of more than 8 lines/Wt. When using the polymer particles as a manufacturing filler, the number content of particles with a diameter exceeding 10μ was further measured using a fine particle size distribution measuring device (measured with a Coulter Counter manufactured by Coulter Electronics). The number of particles is preferably 950 or less per 500,000 particles, and an electrostatic recording material made using acrylonitrile thread polymer particles having such characteristics has a high density recording density of 16 particles/wm. It can be an electrostatic recording medium. Furthermore, the coating film formed by using the acrylonitrile polymer fine particle aggregate of the present invention having the above-mentioned properties as a paint filler has good weather resistance and is free from coating defects such as bulges and fish eyes. be able to. The method for polymerizing the acrylonitrile polymer used in carrying out the present invention is an aqueous suspension polymerization method using a redox polymerization catalyst, or Japanese Patent Application No. 135552/1989, No. 59
-133553, using a peroxide catalyst in an aqueous solvent mixed with a water-soluble organic solvent and water in specific proportions, and using 95 to 100 g of acrylonitrile and 5 gfi1 or less of other copolymerizable vinyl monomers. , reduced viscosity 1.0 to ao, which does not substantially contain sulfonic acid groups
It is better to combine oz. As shown in Figure 1 (a), the polymer obtained by the above 1-polymerization method has a porous structure in which fine primary polymer particles with a particle size of 01 to 2 μm are bonded to each other during the polymerization process, and the volume average particle size is about 20 μm.
It is agglomerated polymer particles of ~40μ. These agglomerated particles cannot be pulverized into a fine particle aggregate having a particle size of 5 μm or less by conventional particle pulverization means such as a ball mill or a hammer mill. The acrylonitrile polymer fine particles of the present invention have a crushing zone that does not have an impact crushing part as shown in FIG. This method efficiently prevents heat generation in the polymer during pulverization, and also reduces the amount of powder generated. The agglomerated polymer particles are very efficiently crushed by the rotational force and the collision force between the powders, and the volume average particle diameter of the present invention is
The number content of particles with diameter t-W exceeding 5μ, 8μ is αaS
S or less, preferably a volume average particle diameter of 1.5 to 4μ, and a particle having a diameter exceeding 8μ, the instructor V ratio is αo. 02%
The following acrylonitrile polymer particle aggregate can be made. FIG. 3(A) is a plan view of the crushing part showing an example of the crushing type crusher used in the present invention, and FIG. 3(B) is a Y-X sectional view. In Fig. 5, α-bar accelerates the circumferential motion of the powder and
α3 is the crushing zone, α◆
is a compressed air inlet for forcing the powder into the grinding zone;
The o3Fi powder supply port, αQ, is a venturi tube for accelerating the powder with compressed air, and (b) is the discharge port for the pulverized fine powder. Furthermore, in the present invention, as shown in FIG. 4, an impact type crusher and a cyclone type classifier are used in combination, and both are used under specific conditions to crush the acrylonitrile polymer particles in a fully open frame. It is possible to obtain an acrylonitrile (acryloni) + full-type 1-coupling machine particle aggregate with the desired performance. FIG. 4('I) is a plan view of a crushing part showing an example of an impact type crusher used in the present invention, and FIG. 4(B) is a sectional view taken along line XX. In Fig. 4, eυ is the jet stream introduction port, 2) is the nozzle injection port, (to) is the raw material powder supply port, (c) is the granule flow rate acceleration section, (a) is the granule crushing impact wall, and It is a crushing and classification chamber,
The above-mentioned impact wall (a) is preferably a rotating ring having a function of rotating in a direction opposite to the flow direction of the jet stream flowing inside the crushing chamber. When using this type of equipment, 200m/86
Acrylonitrile polymer particles are accelerated with a high-speed airflow of 0 or more and collided with the impact crushing wall. It is preferable that the acrylonitrile polymer particles in agglomerated state are completely opened. The flow velocity of the high-speed airflow used here is 200 m
/sea, it tends to be difficult to break up the acrylonitrile polymer particles in the aggregated state,
Only particles having a particle size of 8 μ or more can be obtained with a particle content of 30 or more, and the particle size distribution is extremely large, with a width of 10 or more. On the other hand, by using a high-speed air flow with a flow rate of 200 m/sec or more, the content of particles with a particle size of 5 μ or more can be reduced to 10 to 10.
15%, particle content with particle diameter tV of 8 μ or more is 1 to 5
4, a fine particle aggregate having a volume average particle diameter of 3 to 5 μm can be obtained. The fine particle aggregate thus obtained is processed in a classifier to obtain a particle having the desired volume average particle diameter t- and in which the number content of particles with a particle diameter exceeding 8μ is αaSS or less. . Examples of classifiers include cyclone type, etc.
For example, there is a T-type method in which a crusher and a classifier are combined, that is, the acrylonitrile polymer powder particles are crushed by colliding with each other using a jet stream, and the powder particles in the crushing chamber are classified by centrifugal force caused by rotation. good. Further, in a cyclone type classifier, it is preferable that the fluid velocity in the classification chamber, that is, the velocity of the particle aggregate, be 80 m/sec or more per 01 m of radius t. [Effects of the present invention] The acrylonitrile polymer particles obtained by the present invention have a volume average particle diameter in the range of 1 to 5 μ, and the content of particles with a diameter exceeding 8 μ is below the α05 coefficient, preferably in the volume average The particle size is 1.5 to 4μ, the content of particles with a diameter exceeding 8μ is 102% or less, and in particular, the content of particles with a diameter exceeding 10μ is 50 or less per 500,000 particles measured, preferably Since it is less than 30 pieces, it can be used as a filler.
In particular, it can be effectively used as a filler for electrostatic recording materials with strict requirements. Also,
The acrylonitrile polymer used has 95fil1% of acrylonitrile polymer units and a sulfonic acid group content of cA.
, OX 10-' equivalent/l polymer or less, especially 2X1
By using a 0-' equivalent/l polymer, it has excellent chemical resistance, water resistance, weather resistance, high white discoloration, low specific gravity, and good adhesion with binders. It has been conventionally used as a filler for paints and as a matting agent, and when used in place of inorganic light fillers, it can bring many advantages. Hereinafter, the present invention will be explained in more detail with reference to Examples. [Examples 1 to 6. Comparative Examples 1 to 3 Production of Acrylonitrile Polymer Powder A polyacrylonitrile polymer having a reduced viscosity of 23 was obtained by an aqueous suspension polymerization method. The sulfonic acid group content was t 8 X 10-5 molecules per liter of polymer, and the average particle size was 25μ. Figure 1 shows an enlarged electron microscope photograph of the single coalescing particle obtained (
A). This acrylonitrile polymer particle gold,
Acrylonitrile with an average particle diameter of 20 μm to 55 μm was produced using a pulverizer of the type shown in Figure 4 that crushes powder gold particles by colliding with an impact wall and a Cyclo 7 classifier at the wind speed shown in Table 1. Acrylonitrile polymer powder [1] ~

Obtained [9]. An enlarged photo of the electron environment of the obtained particle aggregate? It is shown in Figure 1 (b). All powder properties were measured and the results are shown in Table 1. Application to recording media> When 50 parts each of acrylonitrile polymer powders [1] to [9] were added to 200 parts of methyl ethyl ketone and dispersed with a stirrer, the acrylonitrile polymer powder was well dispersed in methyl ethyl ketone, and visual inspection showed that no lumps were formed due to the 7 bases kc of the tiers. 40 parts of methyl methacrylate and 6 parts of butyl methacrylate
A 30% toluene solution of an acrylic resin having a co-association ratio of 0 parts was prepared, and a methyl ethyl ketone dispersion of the various acrylonitrile polymer powders was mixed to prepare a dielectric recording material forming solution. The above-mentioned various dielectric recording material forming solutions tl were coated on a base paper treated with polymeric cations and dried to prepare electrostatic recording materials. These electrostatic recording materials have a total surface resistivity of 200, 60% RH,
The results of 100VDCT measurement are shown in Table @2. In addition, from this t'L, 8 lines/Iff+ and 1
All negative signal charges were applied from a fixed multi-head with a linear density of 6 lines/5l II + T, and development with positively charged developing powder was performed.The results of all electrostatic image formation tests are shown in Table 2. . [Comparative Example 4] By aqueous suspension polymerization method, acrylonitrile 93% by weight,
A monopolymer consisting of 7 liters of vinyl acetate was polymerized to obtain acrylonitrile polymer particles having a reduced viscosity of 2.5, a sulfonic acid group content of 2.2×10 −5 equivalents/f polymer, and an average particle diameter of 30 μm. The acrylonitrile polymer particles were supplied to a pulverizer of the type shown in FIG. 3, which pulverizes the powder by colliding it with a granule crushing impact wall, using a high-speed air flow at a flow rate of 230 m/sec to pulverize the particles. Powder with an average particle size of 65μ [10) k
However, it was impossible to pulverize the powder into a powder with a small average particle size. Also, the surface of 8 Song [10] was fused as shown in Figure 2. In addition, for reference, an electrostatic recording material was prepared in the same manner as in Example 1 (Application to electrostatic recording material) using powder [10], and the results of all measurements of its characteristics are shown in Table 2. Indicated. [Examples 7 to 12] The same polymer particles used in Example 1 (Production of Acrylonitrile Polymer Powder) were subjected to collisions between the particles using a jet stream having a crushing zone shown in Figure 3. The mixture was fed to a grinder that grinds and grinds to obtain acrylonitrile polymer powders [11] to [16]. The results of measuring the powder physical properties are shown in Table 3. Further, powders [11] to (16)t- were used, and Example 1
An electrostatic recording medium was prepared in the same manner as in ``Application to electrostatic recording medium'', and its characteristics were measured.The results are shown in Table 4. [Examples 13 to 16] A 2-ton polymerization vessel equipped with a stirrer and a thermometer was purged with nitrogen, and then the charging composition shown in Table 5 was added to start polymerization. From the time when cloudiness was observed in the polymerization system, the following additional solvents were added as shown in Table 5, and after the addition of the additional solvent was completed, the polymerization was continued.
Polymerization was completed after 0 minutes. When the obtained acrylonitrile polymer was separated, washed and dried, the average particle size was 2.
White polymer particles of 0 to 30 μm were obtained. Tokutomo acrylonitrile polymer powder (A
) to (D) were pulverized in the same manner as in Example 1 (Production of Acrylonitrile Polymer Powder) to obtain a fine powder bed of acrylonitrile polymer having an average particle size of 2.0 to 50, and its particle characteristics t -Measurements The results are shown in Table 6. [Examples 17 to 20] Volume average particle size 20 to 20 obtained by the same polymerization method as Example 3
30μ white TL sweetened particles were crushed in the same manner as in Example 7 to obtain a fine powder of acrylonitrile thread polymer with a volume average particle diameter of 2 to 3μ, and the particle characteristics were measured.Results t-Table 7 Show your friends.

[Brief explanation of drawings]

FIG. 1(A) is an enlarged electron microscope photograph of the acrylonitrile thread 1 coalesced particles obtained in the suspension used in the present invention.
FIG. 2B shows an enlarged electron microscope photograph of an acrylonitrile polymer fine particle aggregate of the present invention, and FIG. 2 shows an electron microscope enlarged photograph of polymer particles of a comparative example. FIG. 3 is a schematic diagram of a crushing type crushing apparatus used in carrying out the present invention, in which (a) is a plan view of the crushing sheet, and (b) is a YY cross-sectional view of the supply section. FIG. 4 is a schematic diagram of an impact type crushing device,
(A) is a plan view of the crushing zone, and (B) is its XX sectional view. 11... Compressed air inlet for powder acceleration 13...
- Grinding zone 14... Compressed air inlet for pushing powder 15...
...Powder supply port 16...Venturi tube 17...Discharge port 21 for crushed fine powder...
Jet air flow introduction port 22...Nozzle injection port 23...Raw material powder supply port 24...Particle flow velocity supply port 25...Particle crushing value 's9゜26. ...Crushing and classification room

Claims (6)

[Claims] (1) The copolymerized amount of acrylonitrile is 95% by weight or more, and the reduced viscosity is 1.0, which does not substantially contain sulfonic acid groups.
~8.0 and the volume average particle diameter is 1~5μ
The number content of particles with a diameter exceeding 8μ is 0.05%.
An acrylonitrile polymer fine particle aggregate characterized by the following: (2) The copolymerized amount of acrylonitrile is 95% by weight or more, and the reduced viscosity is 1.0, which does not substantially contain sulfonic acid groups.
Made of a polymer with a volume average particle size of 1.5 to 8.0
4μ, and the number content of particles with a diameter exceeding 8μ is 0.0
The acrylonitrile polymer fine particle aggregate according to claim 1, wherein the acrylonitrile polymer fine particle aggregate is 2% or less. (3) Acrylonitrile produced by aqueous suspension polymerization has a degree of copolymerization of 95% by weight or more, substantially contains no sulfonic acid groups, has a reduced viscosity of 1.0 to 8.0, and has a particle size of 0.1 to 8.0. 2
Acrylonitrile polymer particles with a volume average particle diameter of 10 μ or more, which are agglomerated polymer particles of μ, are pulverized and classified to have a volume average particle diameter of 1 to 5 μ, and the number content of particles with a diameter exceeding 8 μ is 0.05 % or less, a method for producing an acrylonitrile polymer fine particle aggregate. (4) The acrylonitrile polymer powder is accelerated by a jet stream of 200 m/sec or more, supplied to the crushing chamber, and is crushed by colliding with a crushing impact wall in the crushing chamber. A method for producing an acrylonitrile polymer fine particle aggregate as described in 1. (5) A method for producing an acrylonitrile polymer fine particle aggregate according to claim 3, characterized in that the acrylonitrile polymer powder particles are pulverized by colliding with each other in a jet stream. (6) Accelerate the acrylonitrile polymer powder with a jet stream, swirl it in the grinding chamber, collide the acrylonitrile polymer powder particles with each other, and grind them. 4. A method for producing an acrylonitrile polymer fine particle aggregate according to claim 3, which comprises classifying the combined powder.